Depends...I have twin 5 year olds and a soon to be 7 year old...all girls. We thought about taking them, but the twins have grown rather fond of two of the Transformers...and both get messed up pretty badly in the movie. There is also a monster looking scorpion Transformer in the movie. These facts caused us to think again about bringing the girls just to prevent nightmares and the like. BUT I think they will end up seeing it in the not too distant future.
Bottom line, depends on how sensitive your daughters are. The violence is nothing bloody...robots beating up robots. The few times that humans get taken out are fairly bloodless.
I'd say it is up to you, but again it will depend on how sensitive they are.